Even in the earliest moments of his 2012 reelection campaign, Florida Sen. Bill Nelson can see the windup. Twice before Republicans tried to discredit him as a liberal. Twice they failed.

"Facts," Nelson says, "are stubborn things."

But the ground has shifted and Nelson is a bigger target than ever -- Florida's last remaining statewide-elected Democrat, a reliable vote for President Barack Obama and a speed bump in Republican plans to finish the job they started in the midterm elections to seize the Senate.

``Marco Rubio's election showed that Republicans certainly can, if they field a good candidate, pick up that seat,'' said Sen. John Cornyn, the Texan overseeing the GOP's Senate election effort.

One major Republican has entered the race, Florida Senate President Mike Haridopolos. He and other potential rivals have been nipping at Nelson for months.

``He's a very good politician,'' Haridopolos said. ``He sounds like John Wayne. He dresses like a conservative. He votes liberal.''

U.S. Rep. Connie Mack of Fort Myers went a step further and called Nelson ``ultra-liberal'' in a fundraising appeal to Nelson supporters.

``Let's tell the professional politicians like Florida's senior Senator, incumbent Democrat Bill Nelson, that we've seen their liberal record, heard their liberal speeches, and seen their liberal results and we aren't fooled -- and we won't forget.''

In 2000, Nelson faced the same charges from Bill McCollum, and in 2006 it was Katherine Harris who uttered the L word every other breath -- four times in one speech lasting less than four minutes. McCollum came up short and Harris lost by a landslide.